The six Gulf Arab states on Tuesday also urged action to halt mass killings and violations of international law in Syria.

"We ask the international community for serious and swift moves to stop these massacres and these severe attacks that contradict all religions and international laws and humanitarian principles," a communique, issued at the end of a two-day summit of the Gulf Co-operation Council (GCC), read.

Gulf Arab leaders have long called for Syrian President Bashar al-Assad to step down, and in November the GCC recognised a newly formed opposition coalition as the legitimate representative of the Syrian people.